This seems rather suitable for those musing on New Year and resolutions. No more GIFs, many of which still seem to get past GIF-blockers in the form of other formats.
How to hide all animated GIFs in Facebook comments:
This blocking option has been in the FBP Web browser addon since v.29.0 (May 2019), though it’s well-hidden. It’s found in the “Font, Colour & Design” section of the FBP options screen, where almost no-one would think to look for it.
1. Install FBP and re-start the Web browser. Visit Facebook, locate the icon at the top of the Facebook page that launches the FBP control panel.
2. Find and open the “Font, Colour & Design” section on the left-hand side.
3. Tick “Hide Animated Gifs”. Save settings, and exit the control panel.
4. Reload your Web browser and test on an especially annoying Facebook Group. A blank space should replace the animated GIF.
Update: October 2020: no longer working fully. I still see some animated GIFs in comments, despite having FBP working correctly.